This is a problem that some people (at least me) have noticed today after the update of the SecondLife Simulator version to "Second Life Server 1.22.2.89099".
The problem is simple to explain: llSetBuoyancy(); gives unexpected results, at least on attachments. After testing around with it, seems like it does not work correctly when it is set while the avatar is not on air (when "llGetAgentInfo(llGetOwner()) & AGENT_IN_AIR == FALSE").
This mostly effects to avatar movement alteration attachments, such as some flying assistants, jump enhacers or anything that requires turning an avatar into an anti-gravity object, or even, lift it.
When the avatar which the object is attached to is in air, the attachment may start setting buoyancy as wish; it will work, but whenever the avatar lands, the buoyancy function stops working until it reaches again the air and is set there.